C508_01 Datasheet, PDF (22/267 Pages) Infineon Technologies AG – 8-Bit CMOS Microcontroller

C508
Fundamental Structure
Program Status Word
The Program Status Word (PSW) contains several status bits that reflect the current
state of the CPU.
Special Function Register PSW (Address D0_H)
Reset Value: 00_H
Bit No. MSB
LSB
D7_H D6_H D5_H D4_H D3_H D2_H D1_H D0_H
D0_H
CY
AC
F0 RS1 RS0 OV
F1
P PSW
Bit
Function
CY
Carry Flag
Used by arithmetic instructions.
AC
Auxiliary Carry Flag
Used by instructions which execute BCD operations.
F0
General Purpose Flag 0
RS1
Register Bank select control bits
RS0
These bits are used to select one of the four register banks.
RS1
RS0 Function
0
0
Bank 0 selected, data address 00_H-07_H
0
1
Bank 1 selected, data address 08_H-0F_H
1
0
Bank 2 selected, data address 10_H-17_H
1
1
Bank 3 selected, data address 18_H-1F_H
OV
Overflow Flag
Used by arithmetic instructions.
F1
General Purpose Flag 1
P
Parity Flag
Set/cleared by hardware after each instruction to indicate an odd/
even number of “one” bits in the accumulator.
B Register
The B Register is used during multiply and divide and serves as both source and
destination. For other instructions, it can be treated as another scratch pad register.
User’s Manual
2-4
2001-05